Aasa et al: Proc. ICCEM (2012) 167 – 171 [Type text] 167 Thermodynamics Characterization of Density models for an Effective Solar Water Heater Sizing Aasa, S.A, Gbenebor, P.O. and Ajayi, O.O. Department of Mechanical Engineering Covenant University, Otta, P.M.B. 1023 Ogun state Nigeria *Correspondence: oluwashina.gbenebor@covenantuniversity.edu.ng Abstract The problem faced in Sizing of an effective Solar Water Heater (SWH) by engineers to meet certain design requirement is highly enormous. Using the thermodynamic characterization relation and the knowledge of Solar Water Heater (SWH) density’s model; various design were evaluated. The result shows that density model actually predicts adequately and providing alternative means of estimating these design parameters. Also, the properties of the system, such as entropy and enthalpy (specific heat capacities), which cannot be determined directly from experimental axiom, were evaluated. These evaluations therefore, give room to express the thermodynamics properties of the system and consequently improve the design performance. Further comparisons with experimental results reveal a better outfit. Therefore through the knowledge of thermodynamic relation an efficient Solar Water Heater is operated and empirical data is expanded. Key words: Thermodynamic Relation, Density Model, SWH parameters, thermodynamic and dimensionless properties. 1. Introductions Thermosyphon solar water heater is a naturally operated system that performs using the force of gravity. It is the oldest form of the system but less utilized due to its system efficiency. Though it could be highly effective if proper optimized and operated in most temperate developing countries where less power are supplied, low income purchasing for active equipments and less ability to procure require measuring equipment for system optimization; Agbo, (2012). As a result of this; evaluation models are developed to obtain various data whose equipment is not readily available. Density model is one of those models in solar water heater to ease the evaluation of system parameters which are difficult to obtain during experimentations. But despite the use of these models by various researchers, (Aasa and Ajayi 2012, Agbo and Unachukwu 2007), some thermodynamics properties are yet to be evaluated. These parameters, (specific capacity, entropy and enthalpy etc) are of immense important during system optimizations which give us rooms for maneuvering the energy available during the proper system sizing. Further to this, thermodynamics characterizations give room for analysis and calculation of various system parameters which are difficult to obtain during experimentations. Many researchers have used the ability of this skill to obtain parameters that cannot be estimated during the course of experiment. Reiner and Harns, (1994) used the standard formulation of thermodynamic properties to present the fundamental equation of state for helmholtz free energy their results gave a good correlation with the annex 18 research group of IEA. The exergetic evaluation of the thermal performance was also carried out by Gang et al, (2012). In their experiment first and second laws of thermodynamic were employed for optimum determination of the work potential performance. Ma et al, (2010); Liang et al, (2011) and Dufie, (1980) used the energy balance to evaluate the thermal performance of an evacuated tube solar water heater. The high rate of socio political development plays a lot on the need for an improved performance of solar water heater to meet up the